Compounds with the α,β-unsaturated γ-lactone moiety in their structure occur in the plant kingdom, as metabolites of lichens and fungi,1 as sesquiterpene derivatives2 or as steroid glycosides.3 
Natural products possessing this structural element are also components of animal species such as sponges.4 
Many of these compounds exhibit a variety of biologic activities such as antifungal, insecticidal, antibacterial, phytotoxic and anti-inflammatory. Some of them are antibiotics, potential anticancer agents and cyclooxygenase or phospholipase A2 inhibitors.5 
Due to their biological importance, several synthetic methods have been developed for the preparation of α,β-unsaturated γ-lactones. The synthesis of the endocyclic lactones (α,β-butenolides) is reported in the literature, and includes mercuration-carbonylation of propargylic alcohols,6 condensation of 2,5-bis(trimethylsiloxy)furans with carbonyl compounds in the presence of titanium tetrachloride7 and various transformations of C3 synthons, such as, for example, glycidaldehyde.8 
Other references report methods for the synthesis of γ-alkylidene-α,β-butenolides9 and for the preparation of α,β-butenolide derivatives with insect antifeedant activity.10 
A method for the preparation of the exocyclic type lactones involves the reaction of 2-(bromomethyl)acrylic acid in the presence of indium with carbonyl compounds, to give α-methylene-γ-butyrolactones in 7-96% yield.11 
Previous work reports the synthesis of butenolides through the condensation of sugar epoxides with the dianion of phenylselenoacetic acid, followed by hydrolysis and subsequent oxidation of the intermediate phenylselenolactone.12,13,14 The nucleophilic opening of the oxirane is stereospecific, the configuration of the stereogenic centre in the final lactone being determined by the centre of chirality of the starting epoxide.
Another method for the synthesis of α,β-unsaturated γ-lactones involves a Reformatsky type reaction of a ketosugar or a dialdofuranose with ethyl bromomethylacrylate and zinc in THF under reflux.13,14,15 
Ethyl bromomethylacrylate and zinc-silver/graphite at −78° C. have been successfully applied to the synthesis of hydroxyesters from cyclic ketones,16 ketosugars and a 2,3-O-isopropylidene-D-erythronolactone17 and to the synthesis of α,β-unsaturated γ-lactones from some ketosugars.16 
The synthesis of 3-ulosonic acids via a samarium iodide Reformatsky reaction of aldonolactones was also reported.18 
Some of this type of compounds, reported in the literature, have fungicidal efficacy.13 
Epoxy sugars are versatile intermediates in organic synthesis, due to the ease of their preparation from a variety of starting materials and due to their susceptibility to reactions for example with electrophiles, nucleophiles, acids and bases. Furthermore, epoxides are part of a range of compounds recognised as active principles, with biological and pharmacological activity.19 Reference can be made for example to cytotoxic metabolites, namely crotepoxide, pipoxide and senepoxide, the latter playing an important role in plants as an antiparasitic agent.20 
Methods for the preparation of epoxysugars use halohydrins as intermediate compounds,21 and also aminosugars,22 tosylates and/or mesylates,23 vicinal diols,24,25 glycals26 and carbonyl compounds.27 